Struts form class for submissions to edit an item in the current user's cart.
Used for requests to "/CartItemEdit.do".

The validate method of this class extends
CartAddForm.validate(ActionMapping, HttpServletRequest).
It checks the orderItemID property to make sure it exists;
checks the quantity property to make sure it's greater than
zero; and checks to make sure the user's session has not expired. In doing
this, it also populates the orderItem property with the
OrderItem instance being
edited.